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Equity Method Investments - Narrative (Detail) $ in Millions		3 Months Ended		9 Months Ended
	Oct. 03, 2017 USD ($) Employee Location	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method earnings		$ 316	$ 305	$ 1,044	$ 932
The Kraft Heinz Company [Member]
Schedule of Equity Method Investments [Line Items]
Number of shares owned \| shares		325,442,152		325,442,152
Equity method investment ownership percentage		26.70%		26.70%
Equity method investments		$ 17,453		$ 17,453		$ 17,635
Investment in Kraft Heinz common stock - fair value		$ 17,935		17,935		25,306
Equity method earnings				635	800
Common stock dividends received				610	594
Berkadia Commercial Mortgage LLC, Pilot Travel Centers LLC, d/b/a Pilot Flying J, and Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method earnings				$ 409	$ 132
Berkadia Commercial Mortgage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		50.00%		50.00%
Other Assets [Member] \| Berkadia Commercial Mortgage LLC, Pilot Travel Centers LLC, d/b/a Pilot Flying J, and Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 3,600		$ 3,600		$ 3,400
Jefferies Financial Group Inc. [Member] \| Berkadia Commercial Mortgage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		50.00%		50.00%
American Electric Power [Member] \| Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		50.00%		50.00%
Commercial Paper [Member] \| Berkadia Commercial Mortgage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Maximum outstanding balance of commercial paper borrowings		$ 1,500		$ 1,500
Insurance Group [Member] \| Jefferies Financial Group Inc. [Member] \| Berkadia Commercial Mortgage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Reimbursement rate from joint venture partner of Company's surety bond claim losses				50.00%
Berkshire Hathaway Energy Company Subsidiary [Member] \| Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		50.00%		50.00%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member]
Schedule of Equity Method Investments [Line Items]
Number of locations \| Location	750
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Haslam Family [Member]
Schedule of Equity Method Investments [Line Items]
Majority ownership percentage	50.10%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Third Party [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	11.30%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	38.60%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Number of team members \| Employee	28,000
Annual revenues	$ 20,000
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Agreement to Acquire Additional Interest in 2023 [Member] \| Haslam Family [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	20.00%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Agreement to Acquire Additional Interest in 2023 [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of additional interest to be acquired	41.40%